Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$138.34	9.507%	$151.492	$151.49	$151.50	$151.50
Purchase #2	$76.93	12.256%	$86.3585	$86.36	$86.35	$86.40
Purchase #3	$15.78	8.285%	$17.0874	$17.09	$17.10	$17.10
Purchase #4	$84.38	5.795%	$89.2698	$89.27	$89.25	$89.30
Purchase #5	$23.26	13.753%	$26.4589	$26.46	$26.45	$26.50
Purchase #6	$184.56	6.481%	$196.5213	$196.52	$196.50	$196.50
Purchase #7	$132.89	12.590%	$149.6209	$149.62	$149.60	$149.60
7 purchase totals =	$656.14		$716.8088	$716.81	$716.75	$716.90